The present invention, in some embodiments thereof, relates to waste management and, more particularly, but not exclusively, to methods and systems for separating waste material and separated materials produced thereby.
The most common method of disposing of waste material is deposition in landfills. However, environmental concerns and/or the cost of land may render this method unsatisfactory.
Standard recycling of waste material typically requires sorting of waste material into different types of material, and recycling or discarding the different types of material separately.
An alternative to standard recycling is production of refuse-derived fuel (RDF) by shredding and dehydrating solid waste material, and combustion of the RDF in power plants.
U.S. Pat. No. 6,017,475 describes a process of converting household garbage into useful byproducts by reducing the garbage to an aggregate shard, optionally expelling liquid from the aggregate shard, and heating the aggregate shard under pressure to create a pulp. A system comprising a grinder for converting household garbage to an aggregate shard, and a hydrolyzer for decomposing the remaining aggregate shard after the liquid has been removed, to form the pulp, is also described. The process hydrolyzes lignocellulose in the garbage, to obtain an aggregate cellulose pulp having traces of metals and plastics. As further described therein, the aggregate cellulose pulp can be separated into pure cellulose pulp and a residue containing inorganic materials.
U.S. Pat. No. 7,497,335 describes “hydrogravity” separation of a multiple domain solid feedstock to produce particles of each substantially a single domain, each type of particle having a different density. Particles are slurried into a suitable fluid to effect binary separation of the mixture of particles into a stream with a higher average specific gravity and a stream with a lower average specific gravity.
U.S. Pat. No. 6,368,500 describes a system for treatment of collected waste, the system comprising at least one separator for separating between first waste material having a specific gravity equal to or less than that of water and second waste material having a specific gravity above that of water; at least one crusher for producing a liquid product from the first waste material; and acetogenic and methanogenic fermentors for fermenting the liquid product.
International Patent Application having Publication No. WO 2006/035441 describes a method of encapsulating pieces of waste with melted plastic by heating and mixing.
International Patent Application having Publication No. WO 2010/082202 describes a composite material prepared by drying waste, and heating the dried waste while mixing under shear forces. The composite material has thermoplastic properties, and is processed to obtain useful articles.
Additional background art includes International Patent Applications having Publication Nos. WO 2005/077630, WO 2005/092708 and WO 2006/079842; European Patent No. 1711323; KR 2003/0014929; U.S. Pat. Nos. 3,850,771, 4,013,616, 4,772,430, 4,968,463, 5,217,655, 6,017,475, 6,253,527 and 6,423,254; and U.S. patent applications having Publication Nos. 2004/0080072 and 2004/0080072.